linux-kernel - Re: [PATCH net-next,v3] tcp: Set pingpong threshold via sysctl

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Message-ID: <20231016164927.30126-1-kuniyu@amazon.com>
Date:   Mon, 16 Oct 2023 09:49:27 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     <haiyangz@...rosoft.com>
CC:     <corbet@....net>, <davem@...emloft.net>, <dsahern@...nel.org>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <kuniyu@...zon.com>,
        <kys@...rosoft.com>, <linux-doc@...r.kernel.org>,
        <linux-hyperv@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mfreemon@...udflare.com>, <morleyd@...gle.com>,
        <mubashirq@...gle.com>, <ncardwell@...gle.com>,
        <netdev@...r.kernel.org>, <pabeni@...hat.com>, <weiwan@...gle.com>,
        <ycheng@...gle.com>
Subject: Re: [PATCH net-next,v3] tcp: Set pingpong threshold via sysctl

From: Haiyang Zhang <haiyangz@...rosoft.com>
Date: Wed, 11 Oct 2023 13:30:44 -0700
> TCP pingpong threshold is 1 by default. But some applications, like SQL DB
> may prefer a higher pingpong threshold to activate delayed acks in quick
> ack mode for better performance.
> 
> The pingpong threshold and related code were changed to 3 in the year
> 2019 in:
>   commit 4a41f453bedf ("tcp: change pingpong threshold to 3")
> And reverted to 1 in the year 2022 in:
>   commit 4d8f24eeedc5 ("Revert "tcp: change pingpong threshold to 3"")
> 
> There is no single value that fits all applications.
> Add net.ipv4.tcp_pingpong_thresh sysctl tunable, so it can be tuned for
> optimal performance based on the application needs.
> 
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Thanks!